Such a method is already described in French Patent No. 2,674,463 in the name of the applicant company.
According to this method, this grid or perforated plate is fixed by closed-die forging, in particular by cold striking so as to make the metal of said bottom penetrate into the openings in said grid or perforated plate.
By virtue of this method, the perforated plate or grid is firmly embedded into the metal of the bottom of the cooking vessel.
The perforated plate or grid is preferably made of steel, whereas the metal of the cooking vessel is preferably made of aluminum.
Because the grid or perforated plate made of hard metal is embedded in the relatively soft metal of the vessel, the mechanical strength of the bottom of the vessel is considerably improved as regards the various mechanical and thermal stresses to which it is likely to be subjected.
After closed-die forging of the grid or of the perforated plate into the metal of the bottom of the vessel, the plane surface of said bottom usually receives a coating made of non-stick material, such as polytetrafluoroethylene (PTFE) or a coating made of enamel.
Such a coating, especially when it is a PTFE one, is relatively sensitive to scratches due in particular to the use of cutting tools having a sharp-edged blade.
The object of the present invention is especially to overcome the hereinabove drawback.